Purpose: The aim is to qualitatively explore Civics teachers' assessment decisions regarding content, skills, and methods in Swedish upper secondary schools. Methodology: Thematic analyses of assignments and interviews of thirteen Civics teachers in Swedish upper secondary school. Findings: The open Swedish curriculum and Civics syllabus enables teacher agency in assessment decisions and teachers do not find it necessary to assess all content. The thirteen teachers varied their assessment methods, which are mainly chosen from rationales other than measured content and skills. Teacher agency in assessment decisions is affected by teachers' experiences and beliefs, Civics canonic traditions, and context, rather than education or curricular demands, except for a performative discourse focusing on grades. Research limitations/implications: Though limited to a small sample in Swedish upper secondary schools and Civics, findings may be applicable in similar open/flexible subjects and similar national contexts.